Apparatuses and methods for cleaning a substrate

ABSTRACT

A method for cleaning a substrate is provided. The method includes providing foam to a surface of the substrate, brush scrubbing the surface of the substrate, providing pressure to the foam, and channeling the pressured foam to produce jammed foam, the channeling including channeling the pressured foam into a gap, the gap being defined by a space between a surface of a brush enclosure and the surface of the substrate. The brush scrubbing of the surface of the substrate and the channeling of the pressured foam across the surface of the substrate facilitate particle removal from the surface of the substrate.

CLAIM OF PRIORITY

This Application is a Divisional of prior application Ser. No.10/816,337, filed Mar. 31, 2004, now U.S. Pat. No. 7,441,299 whichclaims priority under 35 U.S.C. § 120 as a continuation-in-part of U.S.application Ser. No. 10/746,114, filed Dec. 23, 2003, the disclosure ofwhich is incorporated herein by reference. This application also relatesto U.S. application Ser. No. 10/608,871, filed Jun. 27, 2003, thedisclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to semiconductor manufacturing and, moreparticularly, to apparatuses and methods for use in processing asubstrate.

2. Description of the Related Art

In the fabrication of semiconductor devices, there is a need to performsubstrate (e.g., semiconductor wafer) cleaning. For example, the processof manufacturing electronic devices on semiconductor wafers involves acomplex process of depositing and removing a number of layers.Typically, patterning of layer materials includes the application of anorganic photoresist onto the semiconductor wafer. After plasma chemistryetches a target material, the semiconductor wafer needs to be cleaned toremove the organic photoresist. If the organic photoresist is notremoved, the organic photoresist will contaminate the semiconductorwafer resulting in damage to the electronic devices on the semiconductorwafer. In addition, after a chemical mechanical polishing (CMP)operation, residual particles or films are left on the surface of thesemiconductor wafer. Similarly, these residual particles or films maycause defects such as scratches on the wafer surface which may causedevices on the wafer to become inoperable. To avoid damaging thedevices, the wafer also needs to be cleaned after the CMP operation. Assuch, cleaning operations define a very critical step that is repeatedmany times throughout the process of fabricating semiconductor devices.

FIG. 1 is a simplified side view of a conventional system used to cleansemiconductor wafers. The cleaning system includes two brushes 110configured to receive semiconductor wafer 112 between the brushes. Foam114 is supplied to the surface of semiconductor wafer 112 and brushes110 rotate to scrub the surface of the semiconductor wafer to removeparticles and film. The problem with applying foam 114 in an openenvironment is that the foam haphazardly grows around brushes 110 andcannot be directed to a particular surface area of semiconductor wafer112. In other words, the flow of foam 114 is difficult to control whenapplied in an open environment. Furthermore, different properties offoam 114 result in different cleaning capabilities, and the propertiesof foam 114 are also difficult to control when applied in the openenvironment. The application of foam 114 in the open environment is alsowasteful as a large quantity of the foam is needed to insure a uniformdistribution across the surface of semiconductor wafer 112.

In view of the foregoing, there is a need to conserve the use of foamand to control the physical properties and flow of foam when applied onthe surface of the semiconductor wafer.

SUMMARY OF THE INVENTION

Broadly speaking, the present invention fills these needs by providingapparatuses and methods for cleaning a substrate. It should beappreciated that the present invention can be implemented in numerousways, including as a process, an apparatus, a system, computer readablemedia, or a device. Several inventive embodiments of the presentinvention are described below.

In accordance with a first aspect of the present invention, an apparatusfor use in processing a substrate is provided. The apparatus includes abrush enclosure extending over a length. The brush enclosure isconfigured to be disposed over a surface of the substrate and has anopen region that is configured to be disposed in proximity to thesubstrate. The open region extends over the length of the brushenclosure and enables foam from within the brush enclosure to contactthe surface of the substrate.

In accordance with a second aspect of the present invention, a brushenclosure for use in processing a substrate is provided. The brushenclosure includes an elongated enclosure configured to enclose a brush.The elongated enclosure is configured to be disposed above a surface ofthe substrate and has opposite ends that defines a length. Furthermore,the elongated enclosure has an open region along the length of theelongated enclosure. The open region is configured to be disposed abovethe surface of the substrate and enables a surface of the brush to makecontact with the surface of the substrate.

In accordance with a third aspect of the present invention, a substratecleaning system is provided. The system includes a first brush enclosureand a first brush partially enclosed within the first brush enclosure.The first partially enclosed brush is configured to be disposed above asurface of a substrate. Additionally, the system includes a first driveroller and a second drive roller whereby the first and second driverollers are configured to receive an edge of the substrate to supportand rotate the substrate when placed below the first partially enclosedbrush.

In accordance with a fourth aspect of the present invention, a methodfor cleaning a substrate is provided. In this method, foam is providedto a surface of the substrate. Next, the surface of the substrate isscrubbed with a brush. Pressure is then provided to the foam and thepressured foam is channeled to produce jammed foam. Brush scrubbing thesurface of the substrate and channeling the pressured foam across thesurface of the substrate facilitate particles to be removed from thesurface of the substrate.

Other aspects and advantages of the invention will become apparent fromthe following detailed description, taken in conjunction with theaccompanying drawings, illustrating by way of example the principles ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be readily understood by the followingdetailed description in conjunction with the accompanying drawings, andlike reference numerals designate like structural elements.

FIG. 1 is a simplified side view of a conventional system used to cleansemiconductor wafers.

FIG. 2A is a perspective view of a brush partially enclosed within abrush enclosure, in accordance with one embodiment of the presentinvention.

FIG. 2B is a side view of the brush and the brush enclosure shown inFIG. 2A, in accordance with one embodiment of the present invention.

FIG. 3 is a perspective view of a substrate cleaning system, inaccordance with one embodiment of the present invention.

FIG. 4 is a side view of a partially enclosed brush with foam, inaccordance with one embodiment of the present invention.

FIG. 5A is a magnified side view of the gap region shown in FIG. 4, inaccordance with one embodiment of the present invention.

FIG. 5B is an alternative embodiment of the gap region shown in FIG. 5A.

FIG. 6 is a flowchart diagram of the method operations for cleaning asubstrate, in accordance with one embodiment of the present invention.

DETAILED DESCRIPTION

An invention is disclosed for apparatuses and methods for cleaning asubstrate. In the following description, numerous specific details areset forth in order to provide a thorough understanding of the presentinvention. It will be understood, however, by one of ordinary skill inthe art, that the present invention may be practiced without some or allof these specific details. In other instances, well known processoperations have not been described in detail in order not tounnecessarily obscure the present invention.

The embodiments described herein provide a brush enclosure to enclose abrush and foam. In particular, the brush enclosure is configured tocontain and to control the flow and physical properties of foam. As willbe explained in more detail below, the geometry of the brush enclosurecreates different cleaning effects within the brush enclosure.

FIG. 2A is a perspective view of brush 210 partially enclosed withinbrush enclosure 212, in accordance with one embodiment of the presentinvention. For illustrative purposes, brush enclosure 212 includes acutout section in reference area 220 that shows brush 210 is partiallyenclosed within the brush enclosure. Brush 210 rotates to dislodgeparticles and to sweep the particles away from the surface of asubstrate. Brush enclosure 212 may be configured to enclose any suitablebrush 210 used in processing the substrate. For example, as shown FIG.2A, an exemplary brush 210 has a spline geometry that includes a seriesof parallel, continuous raised strips at right angles to the curvedbrush surface. Another exemplary suitable brush 210 has a knobbygeometry that includes a set of cylinders raised at right angles to thecurved brush surface.

Brush enclosure 212 is an elongated member that extends over length 218.As shown in FIG. 2A, length 218 of brush enclosure 212 extends a lengthof brush 210. However, in another embodiment, length 218 of brushenclosure 212 may be shorter or longer than the length of brush 210.FIG. 2A shows brush enclosure 212 having a tubular shape, in accordancewith one embodiment of the present invention. However, brush enclosure212 may not necessarily have a “tubular” shape, but may be any suitableconfiguration, shape and/or size such as, for example, elongated memberswith rectangular cross sections, elliptical cross sections, triangularcross sections, circular cross sections, etc., as long as the brushenclosure may be configured in a manner that would enable brush 210 tobe partially enclosed.

As will be explained in more detail below, brush enclosure 212 alsoincludes open region 222 and, in one embodiment, additionally includestwo opposing flanges 214 that extend along length and side of openregion 222. Brush enclosure 212 is comprised of a chemically inertmaterial. Exemplary chemically inert materials include plastic, Delrin,polyvinylidene fluoride (PVDF), polyethylene terepthalate (PET), etc.

FIG. 2B is a side view of brush 210 and brush enclosure 212 shown inFIG. 2A, in accordance with one embodiment of the present invention.Here, brush 210 that is partially enclosed within brush enclosure 212 isdisposed above substrate 216. As shown in FIG. 2B, brush enclosure 212includes open region 222 and two opposing flanges 214. Open region 222is configured to be disposed in proximity to a surface of substrate 216and allows a surface of brush 210 to make contact with the surface ofthe substrate. In one embodiment, open region 222 extends along completelength of brush enclosure 212. In another embodiment, length of openregion 222 is less than the length of brush enclosure 212.

Additionally, flanges 214 extend radially outward from an outer surfaceof brush enclosure 212. Each flange 214 extends along the length andalong a side of open region 222. In one embodiment, each flange 214extends along the complete length of open region 222. In anotherembodiment, the length of each flange 214 is less than the length ofopen region 222. Each flange 214 defines a surface that is substantiallyparallel to the surface of substrate 216. As used herein, the term“substantially” means that the angle between the surface of each flange214 and surface of substrate 216 vary from about 0 degrees to about ±45degrees. As shown in FIG. 2B, brush enclosure 212 includes two flanges214 on opposite ends. However, in another embodiment, brush enclosure212 may have one flange 214 instead of two flanges.

FIG. 3 is a perspective view of a substrate cleaning system, inaccordance with one embodiment of the present invention. As shown inFIG. 3, substrate cleaning system includes two brushes 210 partiallyenclosed in brush enclosures 212, two drive rollers 310, and substrate216. Drive rollers 310 receive an edge of substrate 216 to support androtate the substrate. Partially enclosed brushes 210 are orientedrelative to each other such that substrate 216 is received between thebrushes. FIG. 3 shows the use of two partially enclosed brushes 210 toclean substrate 216. However, in another embodiment, one partiallyenclosed brush 210 may be used to clean substrate 216. Additionally, instill another embodiment, the substrate cleaning system includes twobrushes 210, but with one brush partially enclosed in brush enclosure212 and the second brush not enclosed within the brush enclosure.

As will be explained in more detail below, the substrate cleaning systemuses foam to clean substrate 216. A number of bubbles collectively jointo define foam. A bubble is a two-phase system is which gases areenclosed by liquids. The liquids define a membrane or film that holdsand surrounds the gases. In foam, the liquids also exist in the spacebetween the bubbles. In one embodiment, each brush 210 is made of ahigh-porosity foam such as polyvinyl alcohol (PVA) and can be used asfoam generator and foam applicator. To generate foam within brushenclosures 212, gases and liquids are supplied through conduits 312under pressure to brushes 210. The gases and liquids mix within theporous PVA brushes 210 in such a manner to generate foam. In anotherembodiment, pre-generated foam is supplied through conduits 312 tobrushes 210. To spread foam across the entire surface of substrate 216,drive rollers 310 rotate substrate 216. Alternatively, brushes 210 canmove across the surface of substrate 216 to spread foam. Foam mayadditionally be spread by a combination of rotating substrate 216 andmoving brushes 210 across the surface of the substrate.

FIG. 4 is a side view of partially enclosed brush 210 with foam 410, inaccordance with one embodiment of the present invention. As shown inFIG. 4, brush 210 is disposed above substrate 216 and brush enclosure212 partially encloses the brush and foam 410. The enclosure of brush210 and foam 410 creates different zones 412, 414, and 416 of cleaningthe surface of substrate 216. Within the area defined as Zone A 412, thesurface of brush 210 contacts the surface of substrate 216. As brush 210rotates, the brush physically scrubs the surface of substrate 216 toremove particles. As a result, within Zone A 412, the surface ofsubstrate 216 is cleaned by scrubbing.

On the other hand, within the areas defined as Zone B 412, the surfaceof substrate 216 is primarily cleaned by chemical treatment with foam410. Open region 222 of brush enclosure 212 allows foam 410 from withinthe brush enclosure to contact the surface of substrate 216. Asdiscussed above, foam 410 is comprised of liquids and bubbles of gases.When bubbles within foam 410 rupture on the surface of substrate 216,the rupture releases gases and the gases and liquids are placed indirect contact with surface of substrate 216. A chemical reactionbetween the gases, liquids, and surface of substrate 216 occurs therebyfacilitating removal of particles and layer of material (e.g., organicmaterial layer) from the surface of the substrate.

To chemically treat the surface of substrate 216 with foam 410, the gasis preferably a gas or any combination of gases that will chemicallyreact or will facilitate a chemical reaction when placed in directcontact with another material. Exemplary gases that react withcontamination include ozone (O₃), oxygen (O₂), hydrochloric acid (HCl)and hydrofluoric acid (HF), and non-reactive gasses such as nitrogen(N₂) and argon (Ar). The gas may also include any combination of gasessuch as: ozone (O₃) and nitrogen (N₂); ozone (O₃) and argon (Ar); ozone(O₃), oxygen (O₂) and nitrogen (N₂); ozone (O₃), oxygen (O₂) and argon(Ar); ozone (O₃), oxygen (O₂), nitrogen (N₂) and argon (Ar); oxygen (O₂)and argon (Ar); oxygen (O₂) and nitrogen (N₂); and oxygen (O₂), argon(Ar) and nitrogen (N₂). An embodiment of the present invention usesozone as gas because ozone, when combined with water, chemically reactswith an organic material on the surface of substrate 216. The organicmaterial may be an organic photoresist material, which is commonly usedin semiconductor photolithography operations. Nitrogen can be combinedwith ozone to increase the concentration of ozone in the bubbles.

The liquid used to generate foam 310 is a liquid or any combination ofliquids that will chemically react or will facilitate a chemicalreaction when placed in direct contact with another material. The liquidmay be a semi-aqueous or aqueous solution of deionized water (DIW)containing suitable cleaning fluids. Examples of liquids include water(H₂O); deionized water (DIW); water (H₂O) and cleaning fluid; water(H₂O) and surfactant; water (H₂O), cleaning fluid, and surfactant;deionized water (DIW) and surfactant; and deionized water (DIW),cleaning fluid and surfactant. As discussed above, an embodiment of thepresent invention uses water as the liquid because water enables orfacilitates the chemical reaction between ozone and an organicphotoresist material. For more details on foam generation and cleaningsubstrate 216 using foam 410, reference may be made to a U.S. patentapplication Ser. No. 10/608,871 entitled “Method and Apparatus forRemoving a Target Layer from a Substrate Using Reactive Gases,” which isherein incorporated by reference.

Within the areas defined as Zone C 416, the surface of substrate 216 isprimarily cleaned by the attraction of particles to the gas/liquidinterfaces of bubbles. As shown in FIG. 4, the space between the surfaceof each flange 214 and surface of substrate 216 defines gap 224. Gap 224is maintained to induce a non-Newtonian flow field. In one embodiment,dimension of gap 224 ranges from about 0.1 mm to about 5 mm. As usedherein, the term “about” means that the specified dimension or parametermay be varied within an acceptable manufacturing tolerance for a givenapplication. In one embodiment, the acceptable manufacturing toleranceis ±10%.

Pressure is applied to foam 410 within brush enclosure 212 and the foamis channeled into gap 224 (i.e., Zone C 416) to produce jammed foam.Jammed foam is produced by the application of force to compress foam410. When compressed within gap 224, the bubbles within foam 410 deformin shape and rearrange into a more closely packed configuration. Ineffect, the pressure and geometry of gap 224 causes foam 410 to changefrom a meta-stable position to a more stable position within Zone C 416.

As pressure channels foam 410 within brush enclosure 212 through gap224, shear force is created locally between the bubbles of jammed foam.The shear force causes the bubbles to move locally with relationship toeach other. The local movements of bubbles caused by the shear forcerelease bursts of energy, and this energy is transferred to the surfaceof substrate 216 to facilitate the removal of particles from the surfaceof the substrate. Specifically, the bubbles within the jammed foam wantto be at a minimum energy state, where all the angles between thebubbles are approximately 120 degrees. When shear force causes a bubbleat a minimum energy state to pass over another bubble, the anglesbetween the bubbles change, and the change of angle results in a higherenergy state. In effect, a change of angles between bubbles equates to achange of energy. Thus, the energy is released not by bubbles rupturing,but by the local rearrangement of bubbles within the jammed foam. Formore details on the use of jammed foam to clean substrate 216, referencemay be made to a U.S. patent application Ser. No. 10/746,114 entitled“Method and Apparatus for Cleaning Semiconductor Wafers Using Compressedand/or Pressurized Foams, Bubbles, and/or Liquids,” which is hereinincorporated by reference.

As shown in FIG. 4, brush enclosure 212 may additionally includeremoving conduits 450 located within flanges 214, in accordance with oneembodiment of the present invention. Removing conduits 450 areconfigured to remove foam 410, liquid, particles, etc. from surface ofsubstrate 216 by applying vacuum. In another embodiment, conduits 450could also be configured to provide deionized water (DIW) and/orchemical rinse to facilitate foam removal. In still another embodiment,additional conduits 450 may supply an additional chemical and/or gas,such as isopropyl alcohol (IPA), to reduce the surface tension ofliquids on the surface of water as a means of removing the liquid fromthe surface of substrate 216.

FIGS. 5A and 5B are magnified side views of the gap region shown in FIG.4, in accordance with one embodiment of the present invention. As shownin FIGS. 5A and 5B, gap region shows brush 210 disposed above substrate216 partially enclosed within brush enclosure 212. Brush enclosure 212includes flange 214 and the space between the surface of the flange andsurface of substrate 216 defines gap 224. Different gap 224 geometriesmay be used to manipulate the mechanical properties and dimensions offoam 410 and the bubbles within the foam. The combination of changingthe mechanical properties and chemical properties of foam 410 providescleaning process flexibility by changing in-situ properties of the foamfor different cleaning requirements. For instance, as shown in FIG. 5A,a small gap 224 results in small bubbles within the gap. Since gap 224is small, pressure within brush enclosure 212 is large and, as a result,foam 410 exits gap 224 at a high velocity. The combination of smallerbubble size and high foam viscosity increases the shearing force betweenthe bubbles. Higher shearing force results in larger energy transferredto surface of substrate 216 when bubbles within jammed foam locallyrearrange.

On the other hand, as shown in FIG. 5B, a larger gap 224 results inlarger bubbles within the gap. Since gap 224 is large, pressure withinbrush enclosure 212 is less and, as a result, foam 410 exits the gap ata lower velocity. The combination of larger bubble size and lowerviscosity facilitates the removal of particles from vias and trenches.Since different gap geometries create different cleaning properties, thetwo flanges on opposite sides of brush enclosure 212 may be configuredto have different geometries, in accordance with one embodiment of thepresent invention. For example, one flange 214 may be configured to havea small gap to create a higher shear force while the opposite flange 214on the same brush enclosure 212 may be configured to have a larger gapto remove particles from vias and trenches. Thus, in this embodiment,brush enclosure 212 may be configured to satisfy two different cleaningrequirements.

FIG. 6 is a flowchart diagram of the method operations for cleaning asubstrate, in accordance with one embodiment of the present invention.Starting in operation 610, foam is provided to a surface of thesubstrate. At the area where a surface of a brush makes contact with asurface of the substrate, the surface of the substrate is physicallyscrubbed by the brush in operation 612. Simultaneously, within an areacreated by a brush enclosure that is between the area where the brushmakes contact with the surface of the substrate and an area defined by agap, the surface of the substrate is primarily cleaned by chemicaltreatment with foam in operation 613. As discussed above, the chemicaltreatment facilitates the removal of particles and films from thesurface of the substrate by placing gases and liquids, through therupture of bubbles within the foam, in direct contact with the surfaceof substrate. At the same time, pressure is provided to the foam inoperation 614 and, as a result, the pressured foam is channeled toproduce jammed foam in operation 616. In particular, the foam ischanneled into a gap created by the brush enclosure. The gap is definedby a space between a surface of the brush enclosure (e.g., a flange) andthe surface of the substrate. The pressure on the foam and geometry ofthe gap compress the foam to produce the jammed foam. The localrearrangement of bubbles within the jammed foam releases energy thatfacilitates the removal of particles and films from the surface of thesubstrate.

In sum, the above described invention provides apparatuses and methodsfor use in cleaning a substrate. The enclosure of foam reduces theamount of foam needed to cover a particular surface area of thesubstrate. Furthermore, the geometry of the brush enclosure canspecifically direct the flow of foam and control the physical propertiesof foam to better facilitate the removal of particles and film from thesurface of the substrate. As a result, the brush enclosuresimultaneously allows different cleaning actions (e.g., scrubbing,chemical treatment, and rearrangement of bubbles within jammed foam) tobe conducted on a surface area of the substrate.

Although the foregoing invention has been described in some detail forpurposes of clarity of understanding, it will be apparent that certainchanges and modifications may be practiced within the scope of theappended claims. Accordingly, the present embodiments are to beconsidered as illustrative and not restrictive, and the invention is notto be limited to the details given herein, but may be modified withinthe scope and equivalents of the appended claims.

1. A method for cleaning a substrate, comprising: providing foam to asurface of the substrate; brush scrubbing the surface of the substrate;providing pressure to the foam; and channeling the pressured foam toproduce jammed foam, the channeling including channeling the pressuredfoam into a gap, the gap being defined by a space between a surface of abrush enclosure and the surface of the substrate, wherein the brushscrubbing the surface of the substrate and channeling the pressured foamacross the surface of the substrate facilitate particles to be removedfrom the surface of the substrate.
 2. The method of claim 1, furthercomprising: chemically treating the surface of the substrate with thefoam, the chemical treatment facilitating the particles to be removedfrom the surface of the substrate.
 3. The method of claim 2, wherein themethod operation of chemically treating the surface of the substratewith the foam includes, rupturing bubbles within the foam to releasegases and liquids onto the surface of the substrate, the gases andliquids facilitating removal of the particles from the surface of thesubstrate.
 4. The method of claim 3, wherein the gases are defined byone or more of ozone (O₃), oxygen (O₂), hydrochloric acid (HCl),hydrofluoric acid (HF), nitrogen (N₂), and argon (Ar).
 5. The method ofclaim 3, wherein the liquids are defined by one or more of water (H₂O),deionized water (DIW), cleaning fluid, and surfactant.
 6. The method ofclaim 1, wherein the pressure on the jammed foam creates a shear forceon the jammed foam.
 7. The method of claim 1, wherein the methodoperation of providing pressure to the foam includes, applying gases andliquids through a brush, the application of the gases and the liquidsenabling the production of pressure to the foam.